1. Field of the Invention
The present invention relates to a device which detects a particulate matter included in an exhaust gas from a diesel engine or the like.
2. Description of the Related Art
An exhaust gas from a diesel engine or the like includes a particulate matter (PM) detected as three components, that is, an organic solvent soluble component, soot and sulfate, which causes air pollution. In particular, when a defect occurs in a particulate matter generation source such as the diesel engine, the particulate matter in the exhaust gas discharged to the atmosphere increases, and noticeably adversely affects the environment. For the prevention of this problem, it is essential to detect the particulate matter in the exhaust gas and recognize the defect of the diesel engine or the like.
Moreover, in recent years, to prevent environmental pollution and improve the environment, a diesel particulate filter (DPF) for the treatment of the exhaust gas is incorporated and used in an exhaust system or the like. This DPF is generally made of a ceramic material, and can be used with high reliability for a long time. However, it cannot be considered that there is not any possibility that a defect such as a crack is generated owing to thermal deterioration or the like. If the defect is generated, a small amount of particulate matter might leak. For the prevention of this problem, it is important to detect the particulate matter in the exhaust gas treated with the DPF and immediately detect the generation of the defect.
It is to be noted that examples of prior documents include Patent Document 1 (JP-A-60-123761). In Patent Document 1, a particulate matter detection device is disclosed which electrically charges the particulate matter by corona discharge and which measures the ion current of the particulate matter to measure the amount of the particulate matter.